Remote sensing offers water hopes as drought lingers

In the U.S. West and Southwest, large-scale farms struggle to survive economically amid chronic drought conditions and increasing costs for surface water.

Utilizing high tech solutions to improve yield with less irrigation water is a challenge taken seriously by scientists at the USDA Agricultural Research Service’s U.S. Arid Land Agricultural Research Center at Maricopa, Ariz.

Scientists are utilizing an arsenal of high tech remote sensing tools to determine specific plant needs in large-scale production agriculture.

That’s an extreme challenge in the arid U.S. West and Southwest, where large-scale farms struggle to survive economically amid chronic drought conditions and increasing costs for surface water.

Arizona, for example, is in its 15th consecutive year of drought.

Utilizing high tech solutions to improve yield with less irrigation water is a challenge taken seriously by scientists at the USDA Agricultural Research Service’s U.S. Arid Land Agricultural Research Center at Maricopa, Ariz.

“ARS water conservation projects are designed to develop technology to provide farmers with options for limited water to economically continue their enterprises,” says Andy French, ARS research physical scientist.

“ARS’ goal is to find ways to potentially increase the water use efficiency of irrigation by either increased productivity at the current water use level or maintaining productivity with less water.”

The scientists are utilizing an arsenal of high tech remote sensing tools to determine specific plant needs in large-scale production agriculture.

ARS’ toolbox of instruments includes remote sensing cameras, wireless thermal radiometers, scintillometers, and neutron probes to predict and confirm, on a given day, specific field areas where plants need or do not need irrigation water.

This precision technique would allow farmers to irrigate only the areas where water is needed. It would replace the traditional practice of irrigating entire fields according to a calendar, whether plants in each field section need water or not. The scientists began field tests several years ago in three-acre fields of cotton, wheat, and camelina, the latter a new industrial oilseed crop gaining interest in the West as a biofuel.

The cotton trial has taken center stage in the ARS tests since it requires more water than wheat and camelina.

Beginning in 2009, cotton trials were expanded to a 12-acre field to test four irrigation schedule methods. There are 16 cotton borders, with 12 rows per border, which run 600 feet.

Large scale trials in small grains and camelina are planned next year.

Remote sensing

“The solutions found in irrigation could also be applied to increasing crop yields, while minimizing agricultural chemical transport off irrigated fields through site-specific applications of fertilizer and pesticides.”

In the cotton trial, neutron probes record soil moisture and actual crop water use, or evapotranspiration. Soil moisture is measured to three meters under the soil surface. A commercial ETgauge measures plant evaporation at the top of the canopy.

Evapotranspiration is also recorded by micrometeorological stations. Heat shed by plants is calculated by a scintillometer, an instrument that measures shimmering light similar to that seen from heat waves over hot pavement. Wireless-networked thermal radiometers detect crop water stress.

Images from the equipment are collected using a remote sensing system onboard a helicopter flown across the field at two week intervals. It’s hoped the image data can help implement practical and low-cost ways to model crop water use over an entire field.

“The remote sensing system aboard the aircraft includes a multi-spectral camera, which collects light primarily in the red and infrared wavelengths,” French says. “A thermal infrared camera records the surface temperature.”

Remote sensing is hot technology in agriculture worldwide. Future NASA satellites will include advanced sensing technology to more accurately record water use regionally and globally, including on irrigated land.

“Remote sensing information is vital for creating decision support tools which will help farmers achieve long-term prosperity,” French says.

Helicopter use to gather remote sensing data is not practical or affordable for farmers, but it is invaluable for research. Tractor-based and other ground-based sensor systems currently under development can collect remote sensing-like information at much lower costs.

“Hopefully when the dust settles in about 10 years many of the tools and satellite data will be affordable for farmers,” French says.

Encouraging results

“Results suggest farmers can use less water and achieve similar or better yields by scheduling irrigations based on remote sensing observations versus calendar watering,” French says.

“The next step is to improve these methods to achieve similar results consistently for small and large fields, and under normal and water stress conditions.”

Tying all these details together is the challenge for Kelly Thorp, ARS agricultural engineer.

Thorp is working with computer software and complex algorithms to translate the information into practical language that farmers can utilize to make improved bottom line decisions on irrigation and other crop management practices.

“We are really good at collecting data,” Thorp says. “The question is, how do we integrate all of the information to make decisions that improve water use, crop yield, or return on investment? That is the missing piece at this point.”

Another question is, who will actually decipher the information for on-farm use? Farmers already have a long list of daily responsibilities.

“A farmer’s time is limited, and they don’t have much time to review and choose different scenarios on the computer,” says Thorp. “It’s possible that a new industry could evolve to transfer the information into farm-specific use.”

With the inevitability of limited water sources down the road globally, ARS Geneticist Terry Coffelt is testing new crops for arid agriculture production which could replace crops traditionally grown in arid regions. He’s eagerly awaiting test results on 16 varietal lines of camelina, a low water use crop grown mostly as a dryland crop in marginal soil.

Coffelt is also researching guayule, an industrial latex and resin crop, used to make latex rubber gloves for those allergic to Hevea latex.

The scientists concur that the ARS Arizona-based research has great application potential in other regions of the country with different soils, weather conditions, and input requirements.

ARS has labs throughout the nation which could localize the technology to gain widespread benefits.